Visual Perception Flashcards
How does Roth(1986) define Perception?
The Term “Perception” refers to the Means by Which Information Acquired Via the Sense Organs is Transformed Into Experiences of Objects, Events, Sounds, Tastes etc
What does “Visual Perception” refer to?
The Term “Visual Perception” Refers to the Means by Which Information Acquired Via the Eyes Is Transformed Into Experiences of Objects and Events in the Visual World
What is Perceptual Segregation?
The perceptual processes that determine which parts of the visual scene belogn together and which do not.
Name the six original Gestalt Laws, and define them.
Pragnanz Similarity Good Continuation Proximity Familiarity Common Fate
What are the three differences between Figure and Ground
Figure
- Has a distinct form or shape
- In front of ground
- Contour belongs to figure
Ground
- Has no form or shape
- Behind figure
- Has no contour
Define the Doctrine of Isomorphism
The experience of visual organisation is mirrored by a precisely corresponding process in the brain
What did Lashley, Chow, & Semmes(1951) do to investigate the Doctrine of Isomorphism, and what were their findings?
- Placed 4 gold-foil conductors in the visual area of one chimpanzee
- Placed 23 gold pins through the visual cortex of another chimpanzee
- The perceptual ability of the chimpanzees was barely affected.
- Disproves electrical “field force” theory
Name and define the two proposed Gestalt Laws by Rock & Palmer (1990)
- Connected
- Common Region
What are the two purposes of colour vision?
- Distinguish object and background
- Discrimination of finer detail
What are the difference sbetewen rods and cones?
Rods
- 125 million on each retina
- None in fovea
- Specialized for night-time vision
- Specialized for movement detection
- Sensitive to a broad range of wavelengths
Cones
- 6 million on each retina
- Almost all are in fovea
- Specialized for daytime vision
- Specialized for colour vision
- Three types(short, medium , long)
Describe the Young-Helmholtz theory
- Three types of cones
- Short wavelength cones for blue
- Medium wavelength cones for green
- Long wavelength cones for red
- Rare for only one cone type to be active
How does Young-Helmholtz theory explain colour deficiency
- Red/Green deficiency most common because medium and long wavelength cones most likely to be missing or damaged
- Yellow/Blue deficiency least common because short wavelength cones are least likely to be missing or damaged
What are some failures of the Young-Helmholtz theory?
- Failure to fully explain colour deficiency(if someone has no medium wavelength cones, why can’t they see red?)
- Fails to account for negative afterimages
What is the Opponent Process theory proposed by Ewald Hering (1878)?
- There are three types of opponent processes in the visual system
- Red/Green, Blue/Yellow, Black/White
- If a process is inhibited, then the perception of one colour results whereas if it is excited the perception of the other colour results
How did Abramov & Gordon(1994) test the Opponent Process theory?
- Presented observers with individual wavelengths
- Asked to give percentage of red/green/blue/yellow that they perceived
- No reports of simultaneous perception of red and green or of blue and yellow.
How does the Opponent Process theory explain colour deficiency colour deficiency and negative afterimages?
- Red/Green Colour deficient people can’t perceive red or green because Red/Green opponent process disrupted
- Blue/Yellow colour deficient people can’t perceive blue or yellow because blue/yellow opponent process disrupted.
- Adaption occurs during prolonged exposure to a colour stimulus.
- When the stimulus is removed we see the opponent colour.
What Neurophysiological evidence is there for the Opponent Process theory?
De Valois and De valois (1975) located opponent cells in the lateral geniculate nucleous of monkeys
-Transition point of activity of each cell corresponded to a wavelength of light
